In many environments it is desirable to temporarily hold and clamp parts together while other operations, such as drilling and riveting operations, are performed. For example, in the aircraft industry, it is becoming increasingly desirable to perform the drilling of holes and insertion of fasteners using a one-up assembly process. Traditionally, many parts are subject to disassembly after drilling to clean and deburr the parts, resulting in increased labor hours, and often creating damage to the components induced during disassembly and rework associated with mismatched holes after disassembly.
A one-up assembly process, by contrast, involves drilling and fastening multiple layers of a workpiece at one time, without having to disassemble the parts for other operations, such as deburring, cleaning, sealing, and other suitable operations. The layers may be parts of a workpiece that are to be fastened to each other, such as, for example, a skin panel to be fastened to a spar or spar cap, or a skin panel to be attached to a frame of a fuselage. Future production strategies contemplate a “lights out” one-up assembly process, which involves more automation and less human involvement than traditional manufacturing processes.
Tack fasteners are widely used in the aircraft industry to attach the parts of a workpiece together temporarily to perform operations on a workpiece. Since it is time consuming and sometimes difficult (and, therefore, expensive) to fasten parts together temporarily using conventional mechanical devices, such as nuts and bolts, tack fasteners have been developed to avoid these problems.
While various tack fasteners have been developed, “blind” tack fasteners (i.e., fasteners that can be fully installed from a single side of a structural assembly) are frequently desirable, at least in the aircraft industry. Pop rivets and one-sided installation (OSI) bolts are two known types of blind fasteners. Frequently, tack fasteners are made out of relatively soft metals, such as aluminum, to allow the tack fasteners to be removed easily by drilling once the desired operations have been completed on the workpiece. Although tack fasteners made of soft metals can be removed easily, one disadvantage of such tack fasteners is that they may not provide sufficient clamp-up force to attach certain parts together, particularly in an automated one-up assembly process.
In the past, designers have employed various approaches to address this disadvantage. For example, in some cases, such nuts and bolts have been utilized in regions where high clamp-up forces are desired. However, the installation of nuts and bolts is time consuming, and frequently involves the services of two workers, rather than a single worker. Another approach has been to utilize a large number of closely spaced tack fasteners, but this approach often involves many more fasteners and much more labor than desired. Yet another approach has been to utilize tack fasteners made of a harder material, such as steel (e.g., the Blind Bolt marketed by ALLFAST Fastening Systems, Inc. in City of Industry, Calif., or the Maxibolt® Blind Bolt system marketed by Cherry Aerospace in Santa Ana, Calif.). While such tack fasteners may exhibit a higher clamp-up force than aluminum fasteners, the harder material makes the fasteners more difficult to remove by drilling without damaging drill bits.